The Emissivity and Absorptivity of Parachute Fabrics

1959 ◽  
Vol 81 (3) ◽  
pp. 195-200 ◽  
Author(s):  
J. P. Hartnett ◽  
E. R. G. Eckert ◽  
R. Birkebak
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Wave Length ◽  
Radiant Energy ◽  
Temperature History ◽  
Appreciable Amount ◽  
Sufficient Information ◽  
Radiation Properties ◽  
History Of ◽  
Materials Used

The use of parachutes for recovery of information and equipment from high-speed vehicles has directed attention to the heating problem which in some instances may be so severe as to cause destruction of the parachute. Consequently, the parachute engineer requires sufficient information on the heat-transfer characteristics of geometries resembling those of parachutes and on the heat-transfer properties of the materials used to allow a calculation of the temperature history of a descending parachute. In particular, the radiation properties of the parachute materials must be known since the parachute is receiving radiant energy from the sun and loses energy by radiation to the surroundings. The measurement of radiation properties for such parachute materials is more complicated than for solid surfaces since an appreciable amount of energy is transmitted by such fabrics. It is the purpose of this paper to describe the equipment which was used to measure the absorptivity for solar radiation and the long-wave-length emissivity for such parachute materials and to report these data for a number of important parachute materials.

Synchronized High-Speed Video and Infrared Thermometry Study of Bubble Dynamics During Nucleate Boiling of Nanoemulsion

2017 ◽  
Author(s):  
Robert Stephenson ◽  
Jiajun Xu
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Bubble Dynamics ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Heat Diffusion ◽  
Temperature History ◽  
Pure Ethanol ◽  
High Speed Video ◽  
Significant Difference

In this study, a combination of synchronized high-speed video (HSV) and infrared (IR) thermography was used to characterize the nucleation, growth and detachment of bubbles generated during nucleate boiling inside the nanoemulsion fluid. The Ethanol/Polyalphaolefin nanoemulsion fluid was formed by dispersing ethanol nanodroplets into base fluid Polyalphaolefin, in which these nanodroplets can serve as the pre-seed boiling nuclei. With this unique combination, it allows controlled nucleation, time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle to track bubble nucleation and growth. Data gathered included measurements of bubble growth versus time, as well as 2D temperature history of the heater surface underneath the bubbles. Our findings demonstrate a significant difference of bubble dynamics between the nanoemulsion fluid and pure ethanol, which may also account for the substantial increase in heat transfer coefficient and critical heat flux of nanoemulsion fluid. It is also observed here that the bubbles occurred inside the nanoemulsion fluid appear to be more uniform and two orders-of-magnitude larger in size. While the growth rate of the bubbles inside pure ethanol was found to be heat diffusion controlled at a coefficient around ½, which however, dropped to be around 0.3 for nanoemulsion fluid. Further study on this unique system will help reveal its heat transfer mechanisms.

MHF (Minimum Heat Flux) Point on Anodized Zirconium Surface During Quenching

2014 ◽  
Author(s):  
Jun-young Kang ◽  
Seol Ha Kim ◽  
HangJin Jo ◽  
Ho Seon Ahn ◽  
Moo Hwan Kim ◽  
...  
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Visual Observation ◽  
Film Boiling ◽  
Temperature History ◽  
Complete Wetting ◽  
Wetting Contact Angle ◽  
History Of ◽  
Minimum Heat ◽  
Cylindrical Test

Quenching experiment for the evaluation of the Minimum Heat Flux (MHF) point on an anodized zirconium surface was conducted. The anodized zirconium surface showed complete wetting (Contact Angle, ∼ 0°) due to the capillary wicking force by nano- and micro-scaled structures in contrast to bare zirconium surface (∼ 54.3±2°). The cylindrical test sections (bare and anodized zirconium surface) heated up to 800 [°C] by radiation furnace was rapidly immersed into saturated distilled water. The temperature history of the test section showed the enhancement of the MHF point noticeably from 324 [°C] for the bare to 497 [°C] for the anodized zirconium surface. High speed visualization focusing on the interfacial dynamics at the film boiling showed stable wavy motion at the bare zirconium surface. On the contrary, vigorous fluctuation of the liquid-vapor interface on the anodized zirconium surface occurred. The visual observation suggested that it was caused by completely wetting features at the anodized zirconium surface. Therefore, it triggered the enhancement of the MHF point.

Numerical Simulation and Experiment Research on Temperature Field of Steel Slab in Walking Beam Furnace

2011 ◽  
Vol 704-705 ◽  
pp. 412-418 ◽  
Author(s):  
Chao Chen ◽  
Cui Jiao Ding ◽  
De Gang Ouyang ◽  
Zhan Zeng Liu ◽  
Zhong Hua Song ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Temperature Distribution ◽  
Temperature Fields ◽  
Temperature History ◽  
Experiment Research ◽  
Steel Slab ◽  
History Of ◽  
Simulation And Experiment ◽  
Heating Up

This paper presents a study of the temperature fields of steel slab in a walking beam furnace. To simulate the temperature distribution in the slab of heating-up process in heating furnace, a two-dimensional mathematical model was developed. The heat transfer in the furnace was very complex, so the model was developed on the assumptions that the temperature of each section of the furnace was unchangeable, the slab moved in the furnace in even velocity, the heat transfer between the slab and the walking beam was out of consideration, the longitudinal heat conduction of the slab and the effect of the scale on the heat conduction were neglected. The equations were calculated by the finite difference method. A black box experiment research was carried out to measure the temperature history of the slab as it passed through the furnace. The comparison of the calculated results with the measured results showed that the model worked well for simulating the temperature distribution of the slab in walking beam furnace. With this developed model, the optimizing of hot rolling and heating processes of steel slab can be investigated in the future.

An Inverse Analysis Method for Estimation of Heat Flux and Temperature-Dependence of Heat Transfer Coefficient

2011 ◽  
Author(s):  
Shiro Kubo ◽  
Seiji Ioka
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Inverse Method ◽  
Thermal Stresses ◽  
Temperature History ◽  
Inner Surface ◽  
History Of ◽  
Transient Thermal ◽  
The Relationship ◽  
Inverse Analysis Method

Transient thermal stresses develop in pipes during start-up and shut-down. In previous papers the present authors [1–4] proposed an inverse method for determining the optimum thermal inlet liquid temperature history which reduced the maximum transient thermal stress in pipes. The papers considered multiphysics including heat conduction, heat transfer, and elastic deformation. The inverse method used the relationship between inner surface temperature history, transient temperature distribution and transient thermal stresses. The coefficient of heat transfer plays an important role in the evaluation of thermal stress. In this study an inverse method was developed for estimating heat flux and temperature-dependence of the coefficient of heat transfer from the history of the outer surface temperature and the liquid temperature. The method used the relationship between the outer surface temperature and the inner surface temperature. For the regularization of solution the function expansion method was applied in expressing the history of flux on the inner surface. Numerical simulations demonstrated the usefulness of the proposed inverse analysis method. By examining the effect of measurement errors of temperature on the estimation, the robustness of the method was shown.

Design, Fabrication and Calibration of Heat Transfer Gauges for Transient Measurement

2010 ◽  
Author(s):  
Rakesh Kumar ◽  
Niranjan Sahoo ◽  
Vinayak Kulkarni
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Fast Response ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Temperature History ◽  
Heating Rates ◽  
Experimental Conditions

Transient measurements of surface heating rates are very important in many applications in the field of internal combustion engines, gas turbine engines, fluidized beds and high-speed flow environments. In most surface heat transfer mapping, very fast response sensors are used for dynamic temperature measurements in the flow. The surface heat fluxes are then estimated from the temperature history, analytically/numerically by various heat transfers modeling. Thin film gauges and thermocouples are most cost effective temperature sensors for dynamic measurements because the response time of these sensors are in the range of microseconds. The production of heat transfer gauges in the laboratory has always been an art rather than a method of manufacture. The present work is aimed at design and fabrication of fast response thermocouples and thin film gauges (TFG) in the laboratory. Three types of thermocouples have been fabricated (E-type, T-type and K-type) whereas platinum film is deposited on the insulating substrate (Pyrex and Macor) for thin film heat transfer gauge. Both thermocouples and thin film gauges are calibrated under same experimental conditions.

Comments on the Structural Design of High Speed Craft

1995 ◽  
Vol 32 (02) ◽  
pp. 77-100
Author(s):  
Joseph G. Koelbel
Keyword(s):  
Structural Properties ◽  
Structural Design ◽  
High Speed ◽  
Structural Member ◽  
Calculation Methods ◽  
Rough Water ◽  
History Of ◽  
Vertical Accelerations ◽  
Materials Used

A brief discussion of materials used in the construction of small high speed craft is given along with a history of the calculation of hydrodynamic bottom loads. Calculation methods currently in use are reviewed, including those for added drag in waves, vertical accelerations in rough water, total bottom load, load on each structural member, and the required structural properties of the member. In particular, a discussion of the uncertainty inherent in these methods is presented, as well as a recommendation for a somewhat simpler approach which removes some of the uncertainty, and additional recommendations for the improvement of several details of the procedure.

scholarly journals NUMERICAL SIMULATION OF TEMPERATURE DISTRIBUTION ON METAL CASTING IN VERTICAL SOLIDIFICATION

2018 ◽  
Vol 17 (2) ◽  
pp. 80
Author(s):  
G. M. Stieven ◽  
D. R. Soares ◽  
E. P. Oliveira ◽  
E. F. Lins
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Numerical Technique ◽  
Heat Transfer Process ◽  
Temperature History ◽  
Energy Liberation ◽  
Vertical Solidification ◽  
History Of ◽  
Two Phases ◽  
Good Agreement

The metals and alloys solidification can be defined as a transient heat transfer process. A liquid/solid transformation is followed by thermal energy liberation, with a movable boundary separating two phases with different thermophysical properties. The solidification is of great interest to mechanical and chemical engineers. It is a non-linear transient phenomenon, where heat transfer between the casting and the mold plays a important role. This paper aims to propose a study of heat flow from the casting to the mold using a numerical technique to compute the temperature history of all points inside the casting. The cooling process consists of water-cooled mold with heat being extracted only from the bottom, resulting in unidirectional vertical solidification. The ANSYS software was used to obtain the temperature distribution in the casting. Good agreement was obtained when the simulation results were compared with the experimental data.

scholarly journals In-Process Monitoring of Temperature Evolution during Fused Filament Fabrication: A Journey from Numerical to Experimental Approaches

Thermo ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 332-360
Author(s):  
Hamid Reza Vanaei ◽  
Mohammadali Shirinbayan ◽  
Michael Deligant ◽  
Sofiane Khelladi ◽  
Abbas Tcharkhtchi
Keyword(s):  
Heat Transfer ◽  
Temperature Profile ◽  
Process Monitoring ◽  
Alternative Possibilities ◽  
Temperature History ◽  
Layer By Layer ◽  
Fused Filament Fabrication ◽  
Layer Deposition ◽  
Thermally Driven ◽  
History Of

Fused filament fabrication (FFF), an additive manufacturing technique, unlocks alternative possibilities for the production of complex geometries. In this process, the layer-by-layer deposition mechanism and several heat sources make it a thermally driven process. As heat transfer plays a particular role and determines the temperature history of the merging filaments, the in-process monitoring of the temperature profile guarantees the optimization purposes and thus the improvement of interlayer adhesion. In this review, we document the role of heat transfer in bond formation. In addition, efforts have been carried out to evaluate the correlation of FFF parameters and heat transfer and their effect on part quality. The main objective of this review paper is to provide a comprehensive study on the in-process monitoring of the filament’s temperature profile by presenting and contributing a comparison through the literature.

Temperature Variation History Prediction of Fully-Closed Adhesive Joint in Curing Process

2010 ◽  
Vol 44-47 ◽  
pp. 394-399
Author(s):  
Chu Chen ◽  
Zhi Guo Lu ◽  
Jian Ping Lin
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Adhesive Joint ◽  
Temperature History ◽  
Curing Process ◽  
Transfer Coefficients ◽  
Temperature Prediction ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Theory ◽  
History Of

To describe the heat transfer of fully-closed adhesive joint in curing process, adhesive joint, enclosure for closing joints and its inner air are simplified as a multi-lumped-heat-capacity system neglecting the heat from adhesive chemical reaction. Based on heat transfer theory, a temperature prediction model of fully-closed joint was proposed. Combining experimental temperature history of the joint with finite difference method, the combined heat transfer coefficients of adhesive under different curing temperatures were obtained according to Newton's heat transfer formula. And the model was validated by the experiments. The results revealed that the model can be used to predict the temperature of fully-closed adhesive joint in curing process.

Multiple phase transitions investigated by high-speed TEM

1990 ◽  
Vol 48 (4) ◽  
pp. 550-551
Author(s):  
Oleg Bostanjoglo ◽  
Peter Thomsen-Schmidt
Keyword(s):  
Phase Transitions ◽  
High Speed ◽  
Short Exposure ◽  
Semiconductor Film ◽  
Time Resolved ◽  
Short Exposure Time ◽  
Multiple Phase ◽  
Model Substance ◽  
History Of ◽  
Electron Image

Thin GexTe1-x (x = 0.15-0.8) were studied as a model substance of a composite semiconductor film, in addition being of interest for optical storage material. Two complementary modes of time-resolved TEM were used to trace the phase transitions, induced by an attached Q-switched (50 ns FWHM) and frequency doubled (532 nm) Nd:YAG laser. The laser radiation was focused onto the specimen within the TEM to a 20 μm spot (FWHM). Discrete intermediate states were visualized by short-exposure time doubleframe imaging /1,2/. The full history of a transformation was gained by tracking the electron image intensity with photomultiplier and storage oscilloscopes (space/time resolution 100 nm/3 ns) /3/. In order to avoid radiation damage by the probing electron beam to detector and specimen, the beam is pulsed in this continuous mode of time-resolved TEM,too.Short events ( <2 μs) are followed by illuminating with an extended single electron pulse (fig. 1c)

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